In designing a wireless network, a designer will position the base stations such that they will provide optimum coverage and, hence, revenue. The designer must work out a link budget to assure that the wireless subscriber's handset is able to communicate with acceptable quality within the advertised coverage area. This link budget involves determining the optimum number of base stations and the effective radiated power (ERP) of each base station. Since designing a link that would be 100% reliable under all conditions would be cost prohibitive, network providers strive to minimize the drop rate of mobile phone communications to a commercially acceptable level, e.g., 5%. Thus, designers of mobile wireless communication systems typically specify a confidence level, e.g., 95%, of communication link success between the mobile and the base station.
Prior art methods of rating antennas used in mobile wireless communication systems measure the peak or average gain of the antenna only. Additionally, it is common practice to assume a constant gain for both transmit and receive antennas. This assumption is valid for a base station transmit antenna since its position and operating conditions are stable. The receive antenna (such as in a handset or other wireless communication device), however, operates in a much more complicated environment in which reception and transmission conditions vary greatly. First, its orientation in 3-dimensional space is somewhat arbitrary since different users hold the communication device in different orientations (referred to as the "range of talk positions"). Second, what might otherwise be an omni-direction pattern of signal radiation from the mobile antenna becomes a directional pattern because of absorption of the radio signal by the head and hand of the user. Thus, the gain of the handset antenna is a function of both the azimuth angle and the elevation angle, as well as the absorption of the signal by the user.
Previous methods of measuring antenna performance are disclosed, for example, in U.S. Pat. Nos.: 5,233,537; 5,300,939; 5,507,101; 5,548,820; 5,574,981; 5,590,415; 5,670,965; 5,856,809; 5,969,664; and 6,031,498. These and all other patents cited herein are each hereby specifically incorporated herein in their entirety by reference. As mentioned above, all of these previous methods rely upon a measure of the peak or average gain only, which is defined as Peak/ave. However, the peak gain occurs at only one point in space. Thus, there is a need in the field of wireless communications for a method of measuring the performance of antennas such that a power budget can be set to provide a reliable link performance in its operation environment over the intended field of view. Many wireless communication devices are portable and are used in an arbitrary orientation relative a corresponding send/receive station. Therefore, the environmental conditions for the receive antenna can vary greatly. Thus, there is a need in the field of wireless communications for a method of measuring antenna performance wherein the operating angle of the receive antenna relative to the base station varies, reflecting actual operating conditions. Furthermore, prior art methods also assume a constant, omni-directional signal radiation from the handset antenna. However, as explained above, the hand and head of the user absorbs radiation from the handset antenna, thus distorting the pattern of radiation from the handset antenna. Thus, there is a need in the field of wireless communications for a method of measuring the absorption of radiated signal energy by the user's hand and head. The present invention addresses all of these shortcomings of prior art antenna performance measuring systems.